جستجوی مقالات مرتبط با کلیدواژه « نانو سیلیس » در نشریات گروه « مواد و متالورژی »

Epoxy resin has been used as can coating material for decades because of its suitable chemical and mechanical properties compared to the other resins. Recently, usage of this resin has been limited due to the migration of Bisphenol A (BPA) derivatives into the foodstuffs. Different solutions have been proposed to solve this problem, but so far, no suitable, comprehensive and comprehensive answer has been provided. In the current study, coating material containing mixed polyester and epoxy resins with different amounts of nano-silica particles, using Taguchi experimental design method, were prepared. The formulated coating materials were cured in the presence of melamine formaldehyde resin. The mechanical and chemical properties of cured coatings were investigated based on the EN1186-EU 10:2011 standard method. Migration tests containing global migration and BPA migration were performed, and also toxicity assessment showed that the concentrations of released materials into the food simulants were in the acceptable ranges, based on the above-mentioned standard. Also, the results showed that the polyester resin can be a suitable structure for can coatings and replacing it with epoxy resin, up to about 47%, and the presence of silica nanoparticles (about 0.5 wt%), leads to synergistic effects and increases the barrier and protective properties of the modified coatings.

The term " pyroplasticity" refers to the deformation of the white ware that occurs during firing. In particular, this phenomenon is particularly important for tiles fired in roller kiln (especially thin and large dimensions) and the roughness created on the surface by vertical weight. In this study, 1, 3 and 5% of nanosilica and microsilica were replaced in porcelain tile batch. The effect of nano and micro silica on the pyroplasticity, flexural strength and physical properties were investigated. XRD and SEM analyzes were performed on the samples for phase and microstructural studies. The results showed that nano-silica caused more pyroplastic than micro-silica. The results showed that 1% nano silica had the lowest pyroplastic content among samples containing nano silica and micro silica. The results also showed that adding 1% nanosilica increased the flexural strength by 21.18%. The XRD results showed that the highest quartz peak intensities belonged to the microsilica sample and the lowest to the nanosilica sample.

In recent years, geopolymers have received considerable attention because of their properties and potential applications in fire resistant materials, thermal insulation, low-tech building materials, cements and concrete, and etc. Nano silica is a material that can modify mechanical, microstructural, and structural properties of geopolymer products. In this study, nano silica was added to metakaolin-based geopolymer samples at the dosages of 0, 2, 4, and 6 % by weight. Then, mechanical properties of samples such as compressive and flexural strength were measured. The results showed that by increasing the percent of nano silica, both compressive and flexural strength increased from 62.4 to 84.1 and from 13.4 MPa to 24.2 MPa respectively. Also, effect of nano silica on microstructural and structural properties of metakaolin-based geopolymers were investigated using XRD, FTIR, and SEM micro graphs. The SEM micro graphs showed that an increase in the percent of nano silica caused an increase in the homogeneity of samples.

In this paper the thermal stability and properties of resole type phenolic resin is investigated. Thermoset phenolic resins have good physical and mechanical properties up to 250 ˚C temperature; however, for high temperature applications modification of thermal stability of resin is very important. Nano silica (SiO2) effect as a filler on thermal stability of the resin is investigated. Thermal properties was studied by means of thermo gravimetric analysis (TGA) to evaluate char yield and differential scanning calorimetric (DSC) to evaluate the resin curing behavior and SiO2 effects on curing reaction heat. Results showed increase of char yield and curing reaction heat in the presence of SiO2. Fourier transform infrared spectroscopy (FTIR) was used to investigate the variation of absorption bands in the presence of SiO2. The results indicated that with an increase of temperature from 200 ˚C to 800 ˚C resin structure was decomposed and volatile compounds including CH4, CO, CO2 and H2O were released out and the resin was carbonized and converted into amorphous carbon. Finally, the microstructure evolution of modified resin and distribution of nano silica in resin matrix were investigated using scanning electron microscopy (SEM). Results showed that silica particles are completely and uniformly distributed in the resin.